Power driven tamping and ramming device



Dec. 16, 1969 H. HIRN ETAL 3,483,805

POWER DRIVEN TAMPING AND RAMMING DEVICE Filed Nov. '7, 1967 Fig. 7 Fig. 2

WWW W United States Patent 3,483,805 POWER DRIVEN TAMPING AND RAMMING DEVICE Helmut Him, 2 Betzinger Strasse, 7411 Degerschlacht, Germany, and Eberhard Fromm, 66 Alexanderstrasse, 741 Reutlingen, Germany Filed Nov. 7, 1967, Ser. No. 686,366 Int. Cl. EOlc 19/35 US. Cl. 94-49 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a power driven tamping and ramming device of the kind having a reciprocating tool for compacting soil, concrete or similar materials, and more particularly comprising an engine mount integral with a cylinder, a piston connected to said tool and reciprocating within said cylinder, preloaded spring means inserted between the cylinder and the piston for producing the working stroke of the piston, and a cam gear provided between the engine and the tool for engaging the tool during the return stroke.

FIELD OF THE INVENTION The invention resides in the field of devices for ramming and for tamping loose soil, etc. Outstanding features of a device according to the invention are a high compacting force and a smooth and vibration-free running on any soil and with the minimum of etfort to the operator.

DESCRIPTION OF THE PRIOR ART Known devices of the general nature hereinbefore described usually comprise an internal-combustion engine, an engine mount, a cylinder housing, a piston and piston rod located in the housing, spring means between the piston and the cylinder housing, a tamping shoe fixed to the lower end of the piston rod and a gear driven by the engine for imparting a reciprocating motion to the tamping shoe. A prior art construction of a tamping device of this kind provides a cylinder housing connected to the engine mount through a system of parallelogram links, and a crank gear driven by the engine for reciprocating the cylinder housing with respect to the engine mount. The driving power is transmitted from the reciprocating cylinder to the piston and tamping shoe by means of compression springs inserted in the cylinder on both sides of the piston. The shoe with the piston and the springs constitute an oscillatory mechanism vibrating with a frequency equal to the number of revolutions of the crank gear, whereby the tool impacts the soil at each cycle of the vibrating motion.

As the tamping shoe meets the ground near the lower dead center of the motion of the crank gear, the impact velocity and as a result the compaction power of the device are insufiicient.

The known tamping device has the further disadvantage that the natural frequency of the vibrating unit varies with the condition of the soil to be compacted. To adapt the action of the machine to any ground conditions and to find out the most convenient Working range the operator has to exercise a very precise control of the engine speed. Otherwise the action of the device becomes irregular and the amplitude of the oscillations increase, so that at times the device makes uncontrollable bounds. The same difficulties occur at each starting due to resonance between engine speed and natural frequency of the tool.

As the cylinder housing of the known device is reciprocated it is difficult to apply flood lubrication of the moving parts. Either an expensive centralized lubrication system must be applied, or each lubricating point ice has to be attended to separately. At any rate the lubrication depends on the reliability of the operator, a drawback which is not to be under-estimated considering the rugged nature of the building work.

SUMMARY OF THE INVENTION The present invention overcomes the disadvantages of the prior art constructions by providing a power actuated tamping device of the general nature described, having an engine mount fixed to the cylinder in which the tamping piston is reciprocating and wherein preloaded spring means between the cylinder and the piston produce the working stroke of the tamping device, whereas the return stroke is effected by a driving mechanism mounted at the cylinder housing and engaging the tool for producing the return stroke of the tool.

In a device according to the invention the phases of the working stroke and of the return stroke are strictly separated from each other. The working stroke, contrary to the prior art arrangement, no longer constitutes the part of an oscillatory motion, but is determined by the tension of the spring means and the mass of the tool unit, which during the working stroke is accelerated until it strikes the ground with maximum velocity. Thus, the device is capable to impart maximum energy to the ground and develops an outstanding compaction force.

A further feature of the invention is to control the power output of the device by simply providing an installation for varying the pre-load of the spring means.

A further object of the invention is to create a tamping device which works smoothly and maintains its tamping power on any soil.

The invention further contemplates to lOdge the power driven cam mechanism within an enlarged bottom cavity of the engine mount. With this arrangement and due to the absence of vibrations the moving parts of the drive mechanism can be lubricated through an oil sump in the lower part of the housing.

These and other details appear in the following description and in the drawings which show a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a longitudinal partial section through the device taken on the plane II of FIGURE 2, and

FIGURE 2 is a transverse section taken on the plane II-II of FIGURE 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT A driving motor 2 is flanged to an engine mount 1a forming an enlarged portion of a housing 1 which in itself forms a cylinder lodging a reciprocating piston 9. The motor 2 via a pinion 3 and a gear 4 drives a cam plate 5 rotatively mounted within the engine mount. The cam plate is intended to co-operate with a roller 6 mounted for rotation on a piston rod 7, which at its lower end is connected to the tamping shoe 8. The piston rod is axially guided in the cylinder 1 by the piston 9 and in the engine mount 1a by a bearing 10.

A pre-loaded compression spring 11 is inserted between the piston 9 and a spring plate 12. A set screw 13 abuts the spring plate and serves to regulate the pre-load of the spring 11. The circumferential surface of the cam plate is composed of an eccentric portion 5a, a radial or substantially radial portion 5b, and a concentric portion 5c.

The enlarged portion 1a of the housing 1 contains an oil sump 14 for lubricating the tooth gearing 3, 4 and the cam drive 5, 6. The bearing 10 is made up of india rubber or any other suitable elastic material. Both ends of the bearing comprise sealing lips 15 and 16. The upper sealing lip 15 avoids bleeding of oil from the sump 14 through the bearing 10. The lower lip 16 is provided to secure the bearing against penetrating of dirt.

OPERATION OF THE DEVICE When the device is stationary the shoe 8 rests on the ground. The housing 1, 1a is supported by the piston 9 via the spring 11 also during operaion of the device. Appropriately, the pre-load of the spring is large enough so that the cam plate is able to abut the roller. When the cam plate begins to rotate counterclockwise (FIG. 2) and the eccentric portion a contacts the roller 6, the housing 1 with motor 2, gearing 3, 4 and cam plate is lowered and the spring 11 is further compressed. As the surface portion 5a leaves the roller, the spring is released and the housing 1 is launched upwards. Before the housing has fallen back to its initial height the cam plate is carrying out the next revolution. When contacting the roller 6 again the cam lifts the tool unit 7, 8, 9 due to the fact that the mass of the tool unit is substantially smaller than the mass of the housing 1 plus driving unit 2 to 5. As soon as the cam plate 5 again releases the spring 11, the tool is accelerated downwards until it impacts the ground. From this position the tool is again lifted by the eccentric portion of the cam plate, whereas the housing 1 maintains an average level above its stationary position.

For assuring a continuous upward motion of the tool 7, 8, 9 and a smooth action of the device the eccentric portion 5a of the cam plate can be shaped to porduce a sinoidal or any other suitable characteristic of the tool movement.

What is claimed is:

1. A power driven tamping and ramming device working with a reciprocating tool and comprising a cylinder housing carrying a drive motor, means secured to the housing for manually guiding the device, a tool piston telescopically arranged within the housing and connected to a tamping and ramming shoe via a piston rod, a preloaded spring means between the housing and the piston for producing the working stroke of the tool and a driving mechanism mounted at the housing and engaging the tool for producing the return stroke of the tool, said cylinder housing being resiliently supported by the tool via the preloaded spring means.

2. A power driven tamping and ramming device according to claim 1, working with a reciprocating tool and comprising a cylinder housing carrying a drive motor, means secured to the housing for manually guiding the device, a tool piston telescopically arranged within the housing and connected to a tamping and ramming shoe through a piston rod, a preloaded compression spring means between the housing and the piston for producing the working stroke of the tool, a roller mounted on the piston rod, and a cam plate rotated by the drive motor and engaging the roller for producing the return stroke of the tool, the rotary axis of the roller and of the cam plate being parallel to each other and intersecting the longitudinal axis of the tamping tool, said cylinder housing being resiliently supported by the tool via the pre loaded spring means.

3. A power driven tamping and ramming device according to claim 2, the cam plate being rotated by the drive motor through a pinion and a tooth gear.

4. A power driven tamping and ramming device according to claim 2, wherein the surface of the cam plate comprises a curved circumferential .portion offset to the rotation axis of the cam plate, a radial, or approximately radial portion, and a concentric portion, said curved portion being shaped to produce a sinoidal or any other suitable motion establishing a low acceleration of the tool at the beginning of the return stroke.

5. A power driven tamping and ramming device according to claim 2, comprising a spring plate inserted in the upper end of the cylinder housing, the spring means being located between the spring plate and the piston, a screw bolt screwable into the upper part of the housing and abutting the spring plate for adjusting the pre-load of the spring means.

6. A power driven tamping and ramming device according to claim 3, the cylinder housing comprising an enlarged bottom part for lodging pinion and tooth gear, the cam plate and the roller, a bottom wall adapted to serve as an oil sump, and a rubber bushing with a sealing lip on each end for guiding the piston rod in the bottom wall and for avoiding oil leakage from the housing and penetrating of dirt into the housing.

References Cited UNlTED STATES PATENTS 168,245 9/1875 Ferguson 74-55 $44,746 8/ 1895 Ober 9449 1,275,742 8/1918 Pritchard 9449 1,953,825 4/1934 Finley 9449 2,659,281 11/1953 Lucas 94-49 2,888,246 5/1959 Sieber 94-49 X FOREIGN PATENTS 761,036 3/1934 France.

NILE C. BYERS, JR., Primary Examiner 

